This is my build.
I, for one, don’t understand your circuit. So please post a connection diagram. And your sketch.
But if you are powering those servos directly from the Arduino, you’ve been very lucky not to burn it.
The on-board regulators turn off when overheating. You cannot use the Arduino board as a power supply.
What you are describing is probably your power supply collapsing. You can purchase a bunch of Arduinos and keep on going or post an annotated schematic as asked for by others. Be sure to show all connections, power, ground, power sources and note any leads over 25cm/10". Post the capacity of the power sources and voltage.
In your case, the demands of your project, the Arduino 5V output is inadequate. A more capable external power source is required.
